1. Field of the Invention
The present invention relates to a radar apparatus for detecting position information of a target by receiving reflection signals reflected by the target (object) with a plurality of reception antennas.
2. Description of the Related Art
There are known methods for synthesizing an antenna beam by executing digital beam forming on beat signals obtained by a plurality of reception units of a radar apparatus carrying an antenna array including a plurality of reception antenna elements.
For example, JP-A-2001-91617 discloses “a target azimuth detecting apparatus having digital beam forming means for estimating the range of the azimuth of a target using a digital beam forming technique and high-resolution azimuth estimation means for detecting the azimuth of the target by using a high-resolution azimuth detection technique on the estimated azimuth range of the target or a region including the neighborhood of the same”.
JP-A-2001-91617 discloses that “the azimuth of a target can be accurately detected while preventing erroneous detection by a combination of accurate determination of the presence of the target using a digital beam forming (hereinafter also referred to as DBF) technique and accurate detection of the azimuth of the target using the high-resolution azimuth detection technique”.
Specifically, JP-A-2001-91617 describes that an accurate azimuth angle of a target can be obtained by performing DBF on signals obtained by a plurality of reception units (hereinafter referred to as reception channels) to calculate the angle of the target approximately and using more accurate angle measuring means in the neighborhood of the angle obtained by DBF.
In the case of a radar apparatus utilizing DBF as disclosed in JP-A-2001-91617, a higher S/N ratio is achieved, the greater the number of reception channels provided for synthesis using DBF. Thus, higher target detecting performance can be achieved, and resultant synthesized beams become thinner.
The angular resolution of a beam will be higher, the thinner the beam is. However, a great number of beams may be required to obtain a desired range of detection angles, which results in the problem of an increase in the amount of calculation.